3-nitropyridine derivaives and the pharmaceutical compositions containing said derivatives

ABSTRACT

The present invention relates to novel 3-nitropyridine derivatives, pharmaceutically acceptable salts thereof and pharmaceutical compositions containing the same as active ingredients. Methods of preparing the derivatives and pharmaceutical compositions containing the same are also disclosed. The 3-nitropyridine derivatives of the present invention, due to their inhibitory activity against the proliferation of human immunodeficiency virus (HIV) as well as hepatitis B virus (HBV), can be used as therapeutic agents as well as preventive agents for hepatitis B and acquired immune deficiency syndrome (AIDS).

This patent application claims a benefit of priority from Korean Patent Application No. 1999/53295 filed Nov. 27, 1999 and Korean Patent Application No. 1999/64403 filed Dec. 29, 1999 through PCT Application Serial No. PCT/KR00/01365 filed Nov. 27, 2000, the contents of each of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to novel 3-nitropyridine derivatives and the pharmaceutical compositions containing said derivatives. More specifically, the present invention relates to 3-nitropyridine derivatives and their pharmaceutically acceptable salts, represented by the following formula 1, which effectively inhibit proliferation of hepatitis B virus and human immunodeficiency virus. This invention also relates to the process for preparing 3-nitropyridine derivatives and to the pharmaceutical compositions containing said derivatives as effective ingredients against viruses.

Wherein,

R₁ is methoxy or

R₃ is H, hydroxy, dialkylamino group with C₂˜C₆, straight or branched hydroxyalkyl group with C₂˜C₆, straight or branched dihydroxyalkyl group with C₃˜C₆, alkoxyalkyl group with C₃˜C₆, or saturated or unsaturated 5or 6 membered heterocyclic compounds containing 1 to 3 heteroatoms selected from N, O, and S, which may be unsubstituted or substituted with alkyl group of C₁˜C₃; R₃ may or may not contain asymmetrical carbons;

R₄ is H, straight or branched alkyl group with C₁˜C₄, or cycloalkyl group with C₃˜C₆;

R₃ and R₄ both may consist of 5 or 6 membered heterocyclic ring containing 1˜3 heteroatoms selected from N, O, and S, which is unsubstituted or substituted with straight or branched alkyl group with C₁˜C₅, straight or branched hydroxyalkyl group with C₂˜C₅, or hydroxy;

R₂ is indazol-5-yl, or indazol-6-yl;

n is an integer between 0 and 3.

BACKGROUND ART

Hepatitis B virus (HBV; referred as “HBV” hereinafter) causes acute or chronic hepatitis, which may progress to liver cirrhosis and liver cancer. It is estimated that three hundred million people are infected with HBV in the world (Tiollais & Buendia, Sci. Am., 264, 48, 1991). There has been much research about the molecular biological characteristics of HBV and their relationship to liver diseases in order to find ways to prevent and treat hepatitis B. Various vaccines and diagnostic drugs have been developed and much effort is being channeled into research to find treatment for hepatitis B.

HBV genome consists of genes for polymerase (P), surface protein (pre-S1, pre-S2 and S), core protein (pre-C and C), and X protein. Of these proteins expressed from HBV genes, polymerase, surface protein, and core protein are structural proteins and X protein has a regulatory function.

The gene for HBV polymerase comprises 80% of the whole virus genome and produces a protein of 94 kD size with 845 amino acids, which has several functions in the replication of virus genome. This polypeptide includes sequences responsible for activities of protein primer, RNA dependent DNA polymerase, DNA dependent DNA polymerase, and RNase H. Kaplan and his coworkers first discovered reverse transcriptase activities of polymerase, which led to much research in replicating mechanism of HBV.

HBV enters liver when antigenic protein on virion surface is recognized by hepatic cell-specific receptor. Inside the liver cell, DNAs are synthesized by HBV polymerase action, attached to short chain to form complete double helix for HBV genome. Completed double helical DNA genome of HBV produces pre-genomic mRNA and mRNAs of core protein, surface protein, and regulatory protein by the action of RNA polymerase. Using these mRNAs, virus proteins are synthesized. Polymerase has an important function in the production of virus genome, forming a structure called replicasome with core protein and pre-genomic mRNA. This process is called encapsidation. Polymerase has repeated units of glutamic acid at the 3′-end with high affinity for nucleic acids, which is responsible for facile encapsidation. When replicasome is formed, (−) DNA strand is synthesized by reverse transcribing action of HBV polymerase and (+) DNA strand is made through the action of DNA dependent DNA polymerase, which in turn produces pre-genomic mRNAs. The whole process is repeated until the pool of more than 200 to 300 genomes is maintained (Tiollais and Buendia, Scientific American, 264: 48-54, 1991).

Although HBV and HIV are different viruses, the replication mechanisms during their proliferation have some common steps, namely, the reverse transcription of virus RNA to form DNA and the removal of RNA strand from subsequently formed RNA-DNA hybrid.

Recently, nucleoside compounds such as lamivudine and famvir have been reported to be useful inhibitors of HBV proliferation, although they have been originally developed as therapeutics for the treatment of acquired immune deficiency syndrome (AIDS; referred as “AIDS” hereinafter) and herpes zoster infection (Gerin, J. L, Hepatology, 14: 198-199, 1991; Lok, A. S. P., J. Viral Hepatitis, 1: 105-124, 1994; Dienstag, J. L. et al., New England Journal of Medicine, 333: 1657-1661, 1995). However, these nucleoside compounds are considered a poor choice for treatment of hepatitis B because of their high cost and side effects such as toxicity, development of resistant virus and recurrence of the disease after stopping treatment. Effort to find therapeutics for hepatitis B among non-nucleoside compounds has been continued and antiviral effects against HBV have been reported for quinolone compounds (EPO0563732, EPO0563734), iridos compounds (KR 94-1886), and terephthalic amide derivatives (KR 96-72384, KR 97-36589, KR 99-5100). In spite of much effort, however, effective drugs for treating hepatitis B have not been developed yet and therapeutic method mainly depends on symptomatic treatment.

AIDS is a disease inducing dramatic decrease in immune function in the body cells and causing various symptoms of infection rarely seen in normal human beings, which spread to the whole body. Human immunodeficiency virus (HIV; referred as “HIV” hereinafter) responsible for AIDS is known to mainly attack helper T cells, which is one of the T cells with regulatory function in the immune system. When helper T cells are infected with HIV virus and undergo necrosis, human immune system cannot function properly. Impairment in immune function subsequently results in fatal infection and development of malignant tumor. Since AIDS patient has been found in USA in 1981 for the first time, the number increased to more than 850,000 patients in 187 countries in 1993 (WHO 1993 report). WHO predicted that 30 to 40 million more people would be infected with HIV by the year 2000 and 10 to 20 million of them would develop the disease.

At the present time, drugs controlling proliferation of HIV have been most widely used for the treatment of AIDS. Of these, Zidovudine, which had been named Azidothymidine previously, is a drug developed in 1987. Didanosine was developed in 1991 as an alternative medicine for AIDS patients when Zidovudine was either ineffective or could not be used due to side effects. In addition, Zalcitabine was approved for concurrent use with Zidovudine in 1992. These drugs alleviate symptoms, slow down progression of the disease in the infected individuals to full-blown AIDS, and somewhat extend life span in the patients. These drugs, however, are not able to cure the patients completely and often develop problems such as resistance and side effects.

In light of these problems, we, inventors of the present invention, tried to develop therapeutics to treat hepatitis B with little chance of toxicity, side effects, and development of resistant viral strains. We found non-nucleoside compounds with excellent antiviral effect against HBV; synthesized novel 3-nitropyridine derivatives represented in formula 1 and completed the invention by showing their dramatic inhibitory effect on proliferation of HIV as well as of HBV.

DISCLOSURE OF INVENTION

The present invention provides novel 3-nitropyridine derivatives and the pharmaceutical compositions containing said derivatives. More specifically, the present invention provides 3-nitropyridine derivatives and their pharmaceutically acceptable salts, the process for their preparation and the pharmaceutical compositions containing said derivatives as effective ingredient. 3-nitropyridine derivatives of the present invention inhibit proliferation of hepatitis B virus as well as of human immunodeficiency virus and may be effectively used for prevention and treatment of hepatitis B and AIDS.

In order to accomplish the aforementioned goal, the present invention provides novel 3-nitropyridine derivatives represented below in formula 1 and their pharmaceutically acceptable salts.

Wherein,

R₁ is methoxy or

R₃ is H, hydroxy, dialkylamino group with C₂˜C₆, straight or branched hydroxyalkyl group with C₂˜C₆, straight or branched dihydroxyalkyl group with C₃˜C₆, alkoxyalkyl group with C₃˜C₆, or saturated or unsaturated 5 or 6 membered heterocyclic compounds containing 1 to 3 heteroatoms selected from N, O, and S, which may be unsubstituted or substituted with alkyl group with C₁ ˜C₃;

R₃ may or may not have asymmetrical carbons;

R₄ is H, straight or branched alkyl group with C₁˜C₄, or cycloalkyl group with C₃˜C₆;

R₃ and R₄ both may consist of 5 or 6 membered heterocyclic ring with 1 to 3 heteroatoms selected from N, O, and S, which is either unsubstituted or substituted with straight or branched alkyl group with C₁˜C₅, straight or branched hydroxyalkyl group with C₂˜C₅, or hydroxy;

R₂ is indazol-5-yl, or indazol-6-yl;

n is an integer between 0 and 3.

When both R₃ and R₄ are represented as a 5 or 6 membered heterocyclic compounds with 1 to 3 heteroatoms selected from N, O, and S, n equals 0. This heterocyclic ring may be unsubstituted or substituted with straight or branched alkyl group with C₁˜C₅, straight or branched hydroxyalkyl group with C₂˜C₅, or hydroxy group;

When compounds of formula 1 have asymmetrical carbons, they may exist as either R or S optical isomer and the present invention covers both optical isomers and the racemic mixture as well.

Indazol-5-yl and indazol-6-yl groups for R₂ in the present invention are represented in formula 2 and 3 respectively.

Compounds of formula 1 in the present invention may be utilized in the form of salts and the acid addition salts prepared by adding pharmaceutically acceptable free acids are useful. Compounds of formula 1 may be changed to the corresponding acid addition salts according to the general practices in this field. Both inorganic and organic acids may be used as free acids in this case. Among inorganic acids, hydrochloric acid, hydrobromic acid, sulfuric acid, and phosphoric acid may be used. Among organic acids, citric acid, acetic acid, lactic acid, tartaric acid, maleic acid, fumaric acid, formic acid, propionic acid, oxalic acid, trifluoroacetic acid, benzoic acid, gluconic acid, methanesulfonic acid, glycolic acid, succinic acid, 4-toluenesulfonic acid, galacturonic acid, embonic acid, glutamic acid and aspartic acid may be used.

The present invention also provides the process for preparing 3-nitropyridine derivatives of formula 1 as represented in scheme 1.

Wherein, X is Cl or OCH₃; R₂R₃, R₄ and n are as defined in formula 1.

The process of preparation in the present invention comprises the following steps:

(Step 1) Synthesis of 3-nitropyridine derivatives of formula 6 by reacting 2-chloro-3-nitropyridine derivatives of formula 4 with 5-aminoindazole or 6-aminoindazole of formula 5 in a proper solvent under a basic condition at an appropriate temperature;

(Step 2) Synthesis of 3-nitropyridine derivatives of formula 1 by reacting 3-nitropyridine derivatives of formula 6 prepared in step 1 with appropriate amine compounds of formula 7 in a proper solvent under a basic condition at an appropriate temperature.

When R₁ in the compound of formula 1 is a methoxy group, step 1 completes the synthesis of desired compound (X=OCH₃). In this case, the present invention includes the method of preparing 6-methoxy-3-nitropyridine derivatives of formula 6 by reacting 2-chloro-6-methoxy-3-nitropyridine of formula 4 with 5-aminoindazole or 6-aminoindazole of formula 5 in the presence of a base.

Compound of formula 4 in the first step of scheme 1 is 2-chloro-6-methoxy-3-nitropyridine or 2,6-dichloro-3-nitropyridine.

Chemical reagents used in the first and the second steps of scheme 1, namely, 2-chloro-3-nitropyridine derivatives of formula 4, 5-aminoindazole or 6-aminoindazole of formula 5, and amine compounds of formula 7, are commercially available and may be purchased.

Compound of formula 7 in the step 2 above is used to introduce a substituent (R₃—(CH₂)_(n)—NR₄—) into the compound of formula 1 and an appropriate amine compound should be selected depending on the substituent desired, which can be easily done by one with general knowledge in the technical field.

To give more specific details about step 1 in the synthetic process, an organic base may be used and common tertiary amines such as triethylamine, N,N-diisopropylethylamine, N-methylmorpholine, N-methylpiperidine, 4-dimethylaminopyridine, N,N-dimethylaniline, 2,6-lutidine, pyridine are preferable.

Preferable reaction time and temperature are 4˜15 hrs and 20˜60° C.

Preferable for the reaction is a single or a mixture of solvents selected from chloroform, methylene chloride, acetonitrile and alcohols such as methanol and ethanol.

Of 3-nitropyridine derivatives of formula 6 produced in the reaction of step 1, one with chloro group at 6 position is used in the following reaction of step 2.

The reaction in step 2 is described in more detail. Preferable solvent is a single or a mixture of solvents selected from acetonitrile, chloroform, methylene chloride, tetrahydrofuran, N,N-dimethylformamide, N-methylpyrrolidinone, pyridine, water and alcoholic solvents such as methanol, ethanol, and isopropanol.

It is preferable to use excess amount of amine compound (formula7) to increase the efficiency of the reaction. Solvents used in the previous step 1 for the synthesis of 3-nitropyridine derivatives of formula 6 are preferable. Reaction temperature of 25˜80° C. is preferable although it depends on the kind of amine compound used.

In another aspect of this invention, also provided are the pharmaceutical compositions of therapeutics for preventing and treating hepatitis B, which contain 3-nitropyridine derivatives of formula 1 and their pharmaceutically acceptable salts as effective ingredients.

The present invention also provides the pharmaceutical compositions of therapeutics for preventing and treating AIDS, which contain 3-nitropyridine derivatives and their pharmaceutically acceptable salts of formula 1 as effective ingredients.

3-nitropyridine derivatives of formula 1 in this invention have inhibitory effect on proliferation of both HIV and HBV because they interfere with removal of RNA strand from RNA-DNA hybrid formed during the reverse transcription of viral RNA to DNA, which is a common step in the replication mechanism of the two viruses.

Compounds of formula 1 may be taken orally as well as through other routes in clinical uses; for example, it may be administered intravenously, subcutaneously, intraperitoneally, or locally and used in the form of general drugs.

For clinical use of drugs with the pharmaceutical compositions of the present invention, compounds of formula 1 may be mixed with pharmaceutically acceptable excipients and made into various pharmaceutically acceptable forms; for example, tablets, capsules, trochese, solutions, suspensions for oral administration; and injection solutions, suspensions, or dried powder to be mixed with distilled water for the formulation of instant injection solution.

Effective dosage for compound of formula 1 is generally 10˜500 mg/kg, preferably 50˜300 mg/kg for adults, which may be divided into several doses, preferably into 1˜6 doses per day if deemed appropriate by a doctor or a pharmacist.

BEST MODE FOR CARRYING OUT THE INVENTION

Practical and presently preferred embodiments of the present invention are illustrative as shown in the following Examples.

However, it will be appreciated that those skilled in the art, on consideration of this disclosure, may make modifications and improvements within the spirit and scope of the present invention.

PREPARATION EXAMPLE 1 Preparation of 6-chloro-2-(1H-5-indazolylamino)-3-nitropyridine

To the solution of 2,6-dichloro-3-nitropyridine (4 g) and 5-aminoindazole (2.8 g) in acetonitrile (50 ml) was added triethylamine (3.2 ml), and then the solution was reacted at 20-25° C. for 12 hr. The reaction mixture was cooled at room temperature, added H₂O 30 ml slowly, and then reacted at 20° C. for 1 hr. The reaction mixture was filtered, washed with the mixture solution(15 ml) of acetonitrile: H₂O=1:1 (volume ratio) and dried at 50° C. in vacuo to obtain the desired compound (4.7 g, 78%).

m.p.: 233° C. (dec.)

¹H-NMR (DMSO-d₆), ppm: δ 6.94(d, 1H), 7.44(d, 1H), 7.56(d, 1H), 7.91(s, 1H), 8.08 (s, 1H), 8.53(d, 1H)), 10.20(s, 1H)), 13.12(br s, 1H)

PREPARATION EXAMPLE 2 Preparation of 6-chloro-2-(1H-6-indazolylamino)-3-nitropyridine

To the solution of 2,6-dichloro-3-nitropyridine (4 g) and 6-aminoindazole (2.8 g) in acetonitrile (50 ml) was added triethylamine (3.2 ml), and then the solution was reacted at 35-40° C. for 12 hr. The reaction mixture was cooled at room temperature with slowly adding H₂O (20 ml), and then reacted at 20-25° C. for 1 hr. The reaction mixture was filtered, washed with acetonitrile (6 ml) and H₂O (15 ml), and then dried at 50° C. in vacuo to obtain the desired compound (4.4 g, 73%).

m.p.: 234° C. (dec.)

¹H-NMR (DMSO-d₆), ppm: δ 7.02(d, 1H), 7.20(d, 1H), 7.73(d, 1H), 7.99(d, 2H), 8.55(d, 1H), 10.26(s, 1H), , 13.09(s, 1H)

EXAMPLE 1 Preparation of 2-(1H-5-indazolylamino)-6-methoxy-3-nitropyridine

To the solution of 2-chloro-6-methoxy-3-nitropyridine (5 g) and 5-aminoindazole (3.7 g) in methanol (60 ml) was added triethylamine (4.1 ml), and then the solution was reacted at 25-30° C. for 5 hr. The reaction mixture was cooled at room temperature with slowly adding H₂O (30 ml), and then stirred for 0.5 hr. The reaction mixture was filtered, washed with methanol (10 ml), obtained a solid product. The solid product was dried at 50° C. in vacuo to obtain the desired compound (6.5 g, 86%).

m.p.: 206˜208° C.

¹H-NMR (DMSO-d⁶), ppm: δ 3.80(s, 3H), 6.32(d, 1H), 7.55(m, 2H), 8.06(s, 2H), 8.43(d, 1H), 10.52(s, 1H), 13.09(br s, 1H)

EXAMPLE 2 Preparation of 2-(1H-6-indazolylamino)-6-methoxy-3-nitropyridine

To the solution of 2-chloro-6-methoxy-3-nitropyridine (5 g) and 6-aminoindazole (3.9 g) in methanol (60 ml) was added triethylamine (4.1 ml), and then the solution was reacted at 55-60° C. for 14 hr. The reaction mixture was cooled at room temperature, added H₂O 30 mi slowly at 25° C., and then stirred for 0.5 hr. The reaction mixture was filtered, washed with 50% aqueous methanol solution (15 ml) and obtained a solid product. The solid product was dried at 50° C. in vacuo to obtain the desired compound (6.8 g, 90%).

m.p.: 261˜264° C.

¹H-NMR (DMSO-d₆), ppm: δ 3.94(s, 3H), 6.39(d, 1H), 7.24(m, 1H), 7.71(d, 1H), 8.01(s, 1H), 8.19(s, 1H), 8.44(d, 1H), 10.62(s, 1H), 13.04(br s, 1H)

EXAMPLE 3 Preparation of 2-(1H-5-indazolylamino)-6-methyl amino-3-nitropyridine

To the solution of methanol with 40% methylamine (20 ml) was added 2-(1H-5-indazolylamino)-6-methoxy-3-nitropyridine (1 g) obtained by the example 1, and the solution was reacted at 25° C. for 1 hr. The reaction mixture was added H₂O (20 ml) slowly and stirred for 1 hr. The reaction mixture was filtered, washed with 30% aqueous methanol solution (5 ml) and then obtained a solid product. The solid product was dried at 50-60° C. in vacuo to obtain the desired compound (0.82 g, 82%).

m.p.: 238˜240° C.

¹H-NMR (DMSO-d₆), ppm: δ 2.86(d, 3H), 6.09(d, 1H), 7.51(d, 1H), 7.57 (d, 1H), 8.05(t, 2H), 8.24 (d, 2H),10.97(s, 1H), 13.05 (br s, 1H)

EXAMPLE 4 Preparation of 2-(1H-6-indazolylamino)-6-methyl amino-3-nitropyridine

To the solution of methanol with 40% methylamine (20 ml) was added 2-(1H-6-indazolylamino)-6-methoxy-3-nitropyridine (1 g) obtained by the example 2, and the solution was reacted at 25-30° C. for 2 hr. The reaction mixture was cooled and stirred at 20° C. for 0.5 hr. The reaction mixture was filtered, washed with methanol (4 ml) and then obtained a solid product. The solid product was dried at 40° C. in vacuo to obtain the desired compound (0.79 g, 79%).

m.p.: >270° C.

¹H-NMR (DMSO-d₆), ppm: δ 2.98(d, 3H), 6.15(d, 1H), 7.18(d, 1H), 7.69(d, 1), 7.99(s, 1H), 8.09(d, 1H)), 8.35(br s, 1H), 8.44 (s, 1H), 11.14(s, 1H), 13.03(br s, 1H)

EXAMPLE 5 Preparation of 2-(1H-5-indazolylamino)-6-isopropyl amino-3-nitropyridine

To the solution of 2-(1H-5-indazolylamino)-6-methoxy-3-nitropyridine (1 q) obtained by the example 1 in methanol (20 ml) was added isopropylamine (20 ml) slowly and reacted at 45° C. for 20 hr. The reaction mixture was cooled, added H₂O (60 ml) at 25° C. and then stirred for 1 hr. The reaction mixture was filtered, washed with 20% aqueous methanol solution (5 ml) and then obtained a solid product. The solid product was dried at 50˜60° C. in vacuo to obtain the desired compound (1.05 g, 96%).

m.p.: 233˜235° C.

1H-NMR (DMSO-d₆), ppm: δ 1.15(d, 6H), 4.03(m, 1H), 6.06(d, 1H), 7.50(d, 2H), 8.05(m, 2H), 8.15(t, 2H), 10.97(s, 1H), 13.06(br s, 1H)

EXAMPLE 6 Preparation of 2-(1H-6-indazolylamino)-6-isopropyl amino-3-nitropyridine

To the solution of 2-(1H-6-indazolylamino)-6-methoxy-3-nitropyridine (1 g) obtained by the example 2 in methanol (20 ml) was added isopropylamine (20 ml) slowly and reacted at 45° C. for 45 hr. The reaction mixture was cooled and stirred at 25° C. for 1 hr. The reaction mixture was filtered, washed with methanol (5 ml) and then obtained a solid product. The solid product was dried at 40˜50° C. in vacuo to obtain the desired compound (0.95 g, 87%).

m.p.: >270° C.

¹H-NMR (DMSO-d₆), ppm: δ 1.23(d, 6H), 4.17(m, 1H), 6.12(d, 1H), 7.15(d, 1H), 7.68(d, 1H), 8.00(s, 1H), 8.09(d, 1H), 8.28(d, 1H), 8.35(s, 1H), 11.12(s, 1H), 13.08(br s, 1H)

EXAMPLE 7 Preparation of 2-(1H-5-indazolylamino)-6-isobuthyl amino-3-nitropyridine

To the solution of 2-(1H-5-indazolylamino)-6-methoxy-3-nitropyridine (1 g) obtained by the example 1 in methanol (20 ml) was added isobuthylamine (15 ml) slowly and reacted at 45˜50° C. for 20 hr. The reaction mixture was cooled, added H₂O (40 ml) slowly and then stirred at 25° C. for 1 hr. The reaction mixture was filtered, washed with 30% aqueous methanol solution (5 ml), obtained a solid product. The sold product was dried at 50˜60° C. in vacuo to obtain the desired compound (0.95 g, 83%).

m.p.: 230˜232° C.

¹H-NMR (DMSO-d₆), ppm: δ 0.83(d, 6H), 1.83(m, 1H), 3.11(d, 2H), 6.11(d, 1H), 7.50(s, 2H), 7.99(s, 1H), 8.06(d, 1H), 8.19(d, 1H), 8.39(t, 1H), 10.91(s, 1H), 13.07(br s, 1H)

EXAMPLE 8

Preparation of 6-cyclopropylamino-2-(1H-5-indazol ylamino)-3-nitropyridine

To the solution of 2-(1H-5-indazolylamino)-6-methoxy-3-nitropyridine (1 g) obtained by the example 1 in methanol (20 ml) was added cyclopropylamine (10 ml) slowly, heated and reacted at 40˜45° C. for 25 hr. The reaction mixture was cooled with adding H₂O (40 ml) slowly and stirred at 25° C. for 1 hr. The reaction mixture was filtered, washed with 30% aqueous methanol solution (5 ml), obtained a solid product. The solid product was dried at 50° C. in vacuo to obtain the desired compound (0.82 g, 75%).

m.p.: 237˜240° C.

¹H-NMR (DMSO-d₆), ppm: δ 0.56(m, 2H), 0.81(m, 2H), 2.81(br s,1H), 6.06(d,1H), 7.50(d,1H), 7.62(d, 1H), 8.02(s, 1H), 8.09(d, 1H), 8.46(s, 1H), 8.57(s, 1H), 11.02(s, 1H), 13.04(br s, 1H)

EXAMPLE 9 Preparation of 6-amino-2-(1H-5-indazolylamino)-3-nitropyridine

To the solution of 6-chloro-2-(1H-5-indazolylamino)-3-nitropyridine (1 g) obtained by the preparation example 1 in chloroform (20 ml) was added 7 N ammonia solution in methanol (30 ml) and reacted at 35˜40° C. for 15 hr. The reaction mixture was cooled, concentrated under reduced pressure at 25° C. and then precipitated with treatment of methanol (10 ml). The reaction mixture was filtered, which was recrystallised with methanol methylene chloride=4:1 to obtain the desired compound (0.63 g, 67%)

m.p.: 263° C. (dec.)

¹H-NMR (DMSO-d₆), ppm: δ 6.05(d, 1H), 7.48(m, 2H), 7.56(br s, 1H), 7.65(br s, 1H), 8.01 (s, 1H), 8.12 (d, 1H), 8.28 (s, 1H), 10.81(s, 1H), 13.06(br s, 1H)

EXAMPLE 10 Preparation of 6-(2-hydroxyethyl)methylamino-2-(1H-5-indazolylamino)-3-nitropyridine

To the solution of 6-chloro-2-(1H-5-indazolylamino)-3-nitropyridine (1 g) obtained by the preparation example 1 in acetonitrile (20 ml) was added 2-(methylamino)ethanol (1.4ml) and triethylamine (0.6 ml) and then refluxed for 12 hr. The reaction mixture was cooled, precipitated with adding excess H₂O at 20˜25° C., filtered to obtain solid. The above obtained solid was washed with water, dried at 50° C. in vacuo and recrystallised with chloroform:ether=1:3 to obtain the desired compound (0.7 g, 62%).

m.p.: 172˜174° C.

¹H-NMR (DMSO-d6), ppm: δ 3.14(s, 3H), 3.64(m, 4H), 4.80(d, 1H), 6.36(d, 1H), 7.50(s, 2H), 8.02(s, 1H), 8.15(m, 2H), 10.71(d, 1H), 13.03(br s, 1H)

It was prepared compounds in prepared example 11˜30 as the same method used for the example 10. It is shown in Table 1 that the compound name, yield, recrystallizing solution, melting point of compounds in prepared example 11˜30 and 3-nitropyridine derivatives (6) and amine compound (7) as starting materials. It is shown in Table 2 that ^(1H)-NMR of compounds in prepared example 11˜30.

TABLE 1a Compounds Example 3-nitropyridine derivatives (6) amine compound (7) Recrystallising soln Yield (%) m.p. (° C.) 11 6-ethyl-(2-hydroxyethyl)amino-2-(1H-5-indazolylamino)-3-nitropyridine Preparation example 1 2-(ethylamino)ethanol methanol/ether (1:2) 52 164˜166 12 6-[(1S)-1-(hydroxyethyl)ethylamino]-2-(1H-5-indazolylamino)-3-nitropyridine Preparation example 1 (S)-2-amino-1-propanol ethanol 75 >270 13 6-[(1S)-1-(hydroxyethyl)ethylamino]-2-(1H-6-indazolylamino)-3-nitropyridine Preparation example 2 (S)-2-amino-1-propanol ethanol 69 264˜265 14 6-[bis(hydroxymethyl)methylamino)-2-(1H-5-indazolylamino)-3-nitropyridine Preparation example 1 2-amino-1,3-propanediol methanol 80 >270 15 2-(1H-5-indazolylamino)-6-(2-methoxy-1-methyl)ethylamino-3-nitropyridine Preparation example 1 2-amino-1-methoxypropane chloroform/ether (1:5) 58 138˜142 16 6-[2-(dimethylamino)ethylamino]-2-(1H-6-indazolylamino)-3-nitropyridine Preparation example 2 N,N-dimethylethylenediamine methanol/H₂O (1:2) 84 219˜221 17 2-(1H-5-indazolylamino)-6-(4-methyl-1-piperazinyl)amino-3-nitropyridine Preparation example 1 1-amino-4-methylpiperazine mehanol/ether (1:4) 78 170˜174 18 2-(1H-6-indazolylamino)-6-(4-methyl-1-piperazinyl)amino-3-nitropyridine Preparation example 2 1-amino-4-methylpiperazine methanol 56 260 (dec.) 19 2-(1H-5-indazolylamino)-3-nitro-6-(3-pyridyl)methylaminopyridine Preparation example 1 3-(aminomethyl)pyridine methanol/H₂O (1:1) 81 250˜253 20 2-(1H-6-indazolylamino)-3-nitro-6-(3-pyridyl)methylaminopyridine Preparation example 2 3-(aminomethyl)pyridine ethanol 77 >270 21 2-(1H-5-indazolylamino)-3-nitro-6-(4-pyridyl)methylaminopyridine Preparation example 1 4-(aminomethyl)pyridine ethanol/H₂O (2:1) 75 219˜221 22 2-(1H-6-indazolylamino)-3-nitro-6-(2-pyridyl)methylaminopyridine Preparation example 2 2-(aminomethyl)pyridine methanol/ethanol (1:1) 72 256 (dec.) 23 2-(1H-5-indazolylamino)-3-nitro-6-(1-piperazinyl)pyridine Preparation example 1 piperazine ethanol 78 270 (dec.)

TABLE 1b Compounds Example 3-nitropyridine derivatives (6) amine compound (7) Recrystallising soln Yield (%) m.p. (° C.) 24 2-(1H-6-indazolylamino)-3-nitro-6-(1-piperazinyl)pyridine Preparation example 2 piperazine ethanol 88 268 (dec.) 25 2-(1H-5-indazolylamino)-6-(4-methyl-1-piperazinyl)-3-nitropyridine Preparation example 1 1-methylpiperazine methylene chloride/ 63 116˜120 isopropyl ether (1:5) 26 2-(1H-6-indazolylamino)-6-(4-methyl-1-piperazinyl)-3-nitropyridine Preparation example 2 1-methylpiperazine ethanol/H₂O (1:1) 60 253 (dec.) 27 6-[4-(2-hydroxyethyl)-1-piperazinyl]-2-(1H-6-indazolylamino)-3-nitropyridine Preparation example 2 N-(2-hydroxyethyl)piperazine ethanol 82 215˜217 28 6-(4-hydroxy-1-piperidinyl)-2-(1H-5-indazolylamino)-3-nitropyridine Preparation example 1 4-hydroxypiperidine ethanol 76 235˜239 29 6-(4-hydroxy-1-piperidinyl)-2-(1H-6-indazolylamino)-3-nitropyridine Preparation example 2 4-hydroxypiperidine methanol 80 270˜272 30 2-(1H-5-indazolylamino)-6-(4-morpholinyl)amino-3-nitropyridine Preparation example 1 4-aminomorpholine methanol 64 >270

TABLE 2a NMR Example solution ¹H-NMR data (ppm) 11 DMSO-d₆ δ1.09(d, 3H), 3.56(s, 6H), 4.80(d, 1H), 6.35(d, 1H), 7.49(s, 2H), 8.01(s, 1H), 8.15(m, 2H), 10.68(s, 1H), 13.03(br s, 1H) 12 DMSO-d₆ δ1.13(d, 3H), 3.43(t, 2H), 4.01(br s, 1H), 4.81(t, 1H), 6.14(d, 1H), 7.51(t, 2H), 8.01(s, 1H), 8.06(d, 1H), 8.13(d, 1H), 8.20(s, 1H), 10.92(s, 1H), 13.03(br s, 1H) 13 DMSO-d₆ δ1.18(d, 3H), 3.51(m, 2H), 4.13(br s, 1H), 4.81(d, 1H), 6.19(d, 1H), 7.20(d, 1H), 7.69(d, 1H), 8.00(s, 1H), 8.08(d, 1H), 8.25(d, 2H), 11.09(br s, 1H), 13.03(br s, 1H) 14 DMSO-d₆ δ3.54(s, 4H), 4.00(s, 1H), 4.76(s, 2H), 6.21(d, 1H), 7.51(m, 2H), 8.00(s, 1H), 8.06(d, 1H), 8.12(d, 1H), 8.23(s, 1H), 10.93(s, 1H), 13.02(br s, 1H) 15 DMSO-d₆ δ1.12(d, 3H), 3.19(s, 3H), 3.26(m, 1H), 3.37(m, 1H), 4.13(br s, 1H), 6.11(d, 1H), 7.50(s, 2H), 8.00(s, 1H), 8.07 (d, 1H), 8.16(t, 2H), 10.86(s, 1H), 13.06(br s, 1H) 16 DMSO-d₆ δ2.11(s, 6H), 2.45(s, 2H), 3.49(s, 2H), 6.21(d, 1H), 7.23(d, 1H), 7.69(d, 1H), 8.00(s, 1H), 8.09(d, 1H), 8.17(s, 1H), 8.28(br s 1H), 11.04(s, 1H), 13.01(br s, 1H) 17 DMSO-d₆ δ2.30(s, 3H), 2.83(br s, 6H), 3.16(s, 2H), 6.49(d, 1H), 7.50(t, 2H), 8.03(s, 1H), 8.25(t, 2H), 9.15(s, 1H), 10.69(s, 1H), 13.06(s, 1H) 18 DMSO-d₆ + δ2.80(s, 3H), 2.99(br s, 2H), 3.06(br s, 2H), TFA-d₁ 3.23(br s, 2H), 3.46(br s, 2H), 6.54(br s, 1H), 7.27(d, 1H), 7.71(d, 1H), 8.14(s, 1H), 8.26(br s, 2H) 19 DMSO-d₆ δ4.51(s, 2H), 6.18(m, 1H), 7.26(br s, 1H), 7.38(d, 1H), 7.43(d, 1H), 7.51(d, 1H), 7.93(s, 2H), 8.14(d, 1H), 8.42(s, 2H), 8.77(br s, 1H), 10.80(s, 1H), 13.03(br s, 1H) 20 DMSO-d₆ δ4.62(s, 2H), 6.22(d, 1H), 7.15(d, 1H), 7.27(br s, 1H), 7.64(d, 2H), 8.00(s, 1H), 8.15(s, 2H), 8.42(s, 1H), 8.50(s, 1H), 8.80(br s, 1H), 10.99(s, 1H), 13.01(br s, 1H) 21 DMSO-d₆ δ4.51(s, 2H), 6.23(d, 1H), 7.15(s, 2H), 7.32(m, 2H), 7.85(d, 2H), 8.16(d, 1H), 8.43(m, 2H), 8.79(t, 1H), 10.77(s, 1H), 13.01(br s, 1H) 22 DMSO-d₆ δ4.70(s, 2H), 6.30(d, 1H), 7.15(d, 1H), 7.25(m, 2H), 7.58(d, 1H), 7.66(t, 1H), 7.99(s, 1H), 8.06(s, 1H), 8.15(d, 1H), 8.52(d, 1H), 8.85(br s, 1H), 10.98(s, 1H) 12.98(br s, 1H) DMSO: dimethylsulfoxide, TFA: trifluoroacetic acid

TABLE 2b NMR Example solution ¹H-NMR data (ppm) 23 DMSO-d₆ δ2.70(s, 4H), 3.59(s, 4H), 6.46(d, 1H), 7.51(s, 2H), 7.96(s, 1H), 8.03(s, 1H), 8.16(d, 1H), 10.55(s, 1H), 13.07(br s, 1H) 24 DMSO-d₆ δ2.76(s, 4H), 3.66(s, 4H), 6.51(d, 1H), 7.16(d, 1H), 7.69(d, 1H), 8.00(s, 1H), 8.07(d, 1H), 8.20(d, 1H), 10.82(s, 1H), 13.07(br s, 1H) 25 DMSO-d₆ δ2.17(s, 3H), 2.34(s, 4H), 3.65(s, 4H), 6.48(d, 1H), 7.51(t, 2H), 7.96(d, 1H), 8.04(d, 1H), 8.18(d, 1H), 10.59(s, 1H), 13.07 (br s, 1H) 26 DMSO-d₆ δ2.21(s, 3H), 2.40(s, 4H), 3.74(br s, 4H), 6.54(d, 1H), 7.17(d, 1H), 7.70(d, 1H), 8.00(s, 1H), 8.07(d, 1H), 8.22(d, 1H), 10.78(s, 1H), 13.06(br s, 1H) 27 DMSO-d₆ + δ3.19(t, 4H), 3.59(m, 4H), 3.74(t, 2H), TFA-d₁ 4.51(br s, 2H), 6.50(d, 1H), 7.17(d, 1H), 7.69(d, 1H), 8.08(d, 2H), 8.28(d, 1H) 28 DMSO-d₆ δ1.35(m, 2H), 1.76(d, 2H), 3.37(d, 2H), 3.75(br s, 1H), 3.99(br s, 2H), 4.78(s, 1H), 6.50(d, 1H), 7.51(s, 2H), 7.98(d, 1H), 8.02(s, 1H), 8.17(d, 1H), 10.61(s, 1H), 13.05(br s, 1H) 29 DMSO-d₆ δ1.42(m, 2H), 1.82(d, 2H), 3.45(t, 2H), 3.79(br s, 1H), 4.06(br s, 2H), 4.82(s, 1H), 6.55(d, 1H), 7.18(d, 1H), 7.69(d, 1H), 8.00(s, 1H), 8.05(s, 1H), 8.19(d, 1H), 10.81(s, 1H), 13.06(s, 1H) 30 DMSO-d₆ δ2.77(s, 4H), 3.68(s, 4H), 6.55(s, 1H), 7.50(t, 2H), 8.02(s, 1H), 8.25(t, 2H), 9.12(s, 1H), 10.67(s, 1H), 13.04(s, 1H) DMSO: dimethylsulfoxide, TFA: trifluoroacetic acid

<Experiment 1> Inhibitory Effect on the In Vitro Activities of HBV Polymerase in Reverse Transcription

The following in vitro experiment was performed to determine the effect of the compounds of formula 1 on the activity of HBV polymerase during reverse transcription.

The present inventors submitted application for a patent concerning HBV polymerase genetically expressed in and separated from E.coli, the process of its preparation, and the method to measure the enzyme activities (KR 94-3918, KR 96-33998). In the present experiments HBV polymerase was used which had been expressed in E. coli as stated above.

The method used in the present invention to measure in vitro reverse transcribing activities of HBV polymerase is as follows. Basic principles are the same as for ELISA. Nucleotides with biotin or digoxigenin group attached are included as substrates and anti-DIG antibodies attached to peroxidase enzyme recognize the polymerized substrates.

To the wells coated with streptavidin, 20 μl of HBV polymerase, 20 μl of reaction mixture (10 μM each of DIG-UTP and Biotin-UTP, 46 mM Tris-HCl, 266 mM KCl, 27.5 mM MgCl₂, 9.2 mM DTT substrate/primer nybrid), and 20 μl of test compound (added to 1, 0.1, and 0.01 μg/ml) were added and allowed to react at 22° C. for 15 hrs. During this reaction, HBV polymerase catalyzes DNA synthesis and digoxigenin and biotin attached to nucleotides form bonds with streptavidin coated on the bottom of wells. When the reaction was done, each well was washed with 250 μl of cleaning buffer (pH 7.0) for 30 seconds, which was repeated five times to remove remaining impurities. 200 μl of anti-DIG-POD antibody was added to each well and allowed to react for 1 hr at 37° C., and the wells were washed with cleaning buffer to remove impurities. 200 μl each of ABTS™, a substrate of peroxidase, was then added and allowed to react at room temperature for 30 min. Absorbance was measured at 405 nm using ELISA reader.

The percentage of reduction in HBV polymerase activities for reverse transcription was calculated using the group without test compound as a control and the results are shown in Table 3.

TABLE 3a Effect on the HBV polymerase activities in reverse transription Inhibition activity on HBV-RT (%) Compound 1 μg/ml 0.1 μg/ml 0.01 μg/ml Example 1 85 54 30 Example 2 76 50 12 Example 3 58 47 20 Example 4 60 51 26 Example 5 96 87 53 Example 6 91 76 49 Example 7 95 80 47 Example 8 72 52 38

TABLE 3b Effect on the HBV polymerase activities in reverse transription Inhibition activity on HBV-RT (%) Compound 1 μg/ml 0.1 μg/ml 0.01 μg/ml Example 9 80 59 40 Example 10 78 58 50 Example 11 85 60 35 Example 12 90 56 38 Example 13 66 35 10 Example 14 85 49 30 Example 15 97 68 47 Example 16 80 55 38 Example 17 75 52 41 Example 18 70 43 25 Example 19 91 58 42 Example 20 66 40 21 Example 21 94 65 45 Example 22 81 60 49 Example 23 96 66 51 Example 24 62 43 20 Example 25 88 54 35 Example 26 63 40 18 Example 27 60 38 15 Example 28 55 34 20 Example 29 52 35 10 Example 30 71 49 32

As shown in Table 3, compound of the present invention have excellent inhibitory effects on the HBV polymerase activities with more than 90% inhibition at the concentration of 1 μg/ml. Moreover, compounds of the present invention are not expected to have problems such as toxicity and development of resistant viruses as observed in the use of nucleosides and maybe applied together with nucleoside compounds due to different mechanisms of action.

In summary, compounds of the present invention effectively reduce the activities of HBV polymerase, inhibit replication and proliferation of HBV and may be useful as therapeutics for prevention and treatment of hepatitis B.

<Experiment 2> Inhibitory Effect on the Proliferation of HBV in HBV Producing Cell Line

The following experiment was performed to determine inhibitory effects of compounds of formula 1 on the proliferation of HBV producing cell line.

To test for antiviral effect, replication and proliferation of HBV were measured in HepG 2.2.15, a human liver cancer cell line.

The cell concentration was adjusted to 1×10⁵ cells/ml and 1 ml was added to each well of a 24-well cell culture plate, which was then kept in a culture box for 3-4 days at 37° C. under 5% CO₂ until cells grew sufficiently, changing culture medium everyday. When the cells matured sufficiently, the test compounds were added to the final concentrations of 0.01, 0.1, and 1 μg/ml. One week after the addition of test compounds, the culture solution was centrifuged at 5,000 rpm for 10 min. 25 μl of supernatant was transferred to a new tube and 5 μl of lysis solution [0.54N NaOH, 0.06% NP40] was added to each tube. After keeping the tube at 37° C. for 1 hr, 30 μl of neutralizing solution [0.09N HCl 0.1MTris-HCl, pH7.4] was added as a reaction solution for competitive polymerase chain reaction (PCR).

PCR was performed using genetic sequence of HBV core protein as a matrix. PCR reaction was carried out by adding 1 unit of Taq polymerase enzyme to 25 pmol of each primer, 250 μM dNTP, 5 μl of PCR reaction solution [0.54N NaOH, 0. 06% NP40, 0.09N HCl, 0.1M Tris-HCl, pH 7.4].

DNA polymerized by PCR was electrophoresed on Agarose gel and quantitatively analyzed using an image analyzer (Gel Doc 1000, Bio-Rad) in order to evaluate the effect of compounds of the present invention on the reduction of HBV proliferation.

3TC (lamivudine) was used as a positive control at the same concentrations as those of the test compounds. The percentage of reduction in HBV proliferation was calculated using the group without test compound as a control and the results are represented in Table 4.

TABLE 4 Inhibitory effect on the HBV proliferation Inhibition activity on HBV-RT (%) Compound 1 μg/ml 0.1 μg/ml 0.01 μg/ml Example 1 82 45 20 Example 2 72 40 — Example 3 53 35 — Example 4 58 40 — Example 5 94 81 41 Example 6 90 72 33 Example 7 93 75 30 Example 8 65 46 25 Example 11 83 45 20 Example 12 85 48 29 Example 14 80 41 22 Example 15 95 60 36 Example 19 85 51 30 Example 21 90 50 33 Example 23 92 55 35 Example 25 83 46 25 3TC 99 80 48

As shown above in Table 4, non-nucleoside compounds of the present invention have excellent inhibitory effect on the HBV polymerase activities in reverse transcription with more than 80% reduction of HBV proliferation at the concentration of 1 μg/ml. Moreover, compounds of the present invention, being non-nucleosides, may not have problems such as toxicity and early development of resistant virus strains observed in the use of nucleoside substances. It is also expected that compounds of the present invention may be used in parallel with nucleoside compounds since the former act on allosteric binding pockets while the latter act in the domain of polymerase activities.

As described above, compounds of the present invention have excellent inhibitory effect on the HBV polymerase activities important in reverse transcription step of HBV replication. Based on the mechanism, these compounds are able to effectively control HBV proliferation and may be useful as therapeutics for prevention and treatment of hepatitis B.

<Experiment 3> Inhibitory Effect on the In Vitro HIV Enzyme Activities in Reverse Transcription

The following in vitro experiments were done to determine the effect of compounds of formula 1 on the reduction of HIV enzyme activities in reverse transcription.

Non-radioactive reverse transcriptase assay kit (Boehringer Mannheim) was used in the measurement of in vitro transcriptase activities. 20 μl (40 ng) of HIV transcriptase and 20 μl of reaction mixture containing matrix-primer hybrid poly(A)oligo(dT)₁₅, DIG(digoxigenin)-dUTP, biotin-dUTP, and TTP were added to wells coated with streptavidin. Test compounds were also added at the final concentrations of 0.1 and 1 μg/ml and allowed to react at 37° C. for 1 hr. At this time, DNA is formed from RNA by the action of HIV reverse transcriptase, forming bonds with streptavidin coated on the bottom of wells because of digoxigenin and biotin moieties attached to nucleotides.

When the reaction was completed, each well was washed with 250 μl of cleaning buffer (pH7.0) for 30sec. five times to remove remaining impurities. 200 μl of anti-DIG-POD antigen was added to each well, allowed to react at 37° C. for 1 hr and washed as above to remove impurities. 200 μl of ABTS™, a substrate for peroxidase, was added to each well and allowed to react at room temperature for 30 min. Absorbance at 405 nm was then read for each solution using ELISA reader and used for quantitative determination of inhibitory effect on the HIV transcriptase activities. The percentage of reduction in the activities of HIV reverse transcriptase was calculated using the group without test compound as control and the results are represented in Table 5.

TABLE 5 Inhibitory effect on the activities of HIV reverse transcriptase Inhibition activity on HBV-RT (%) Compound 1 μg/ml 0.1 μg/ml Example 1 75 35 Example 4 70 51 Example 5 55 20 Example 6 69 50 Example 7 72 45 Example 11 67 46 Example 12 64 40 Example 14 59 44 Example 16 75 51 Example 20 84 53 Example 21 72 39 Example 27 81 45

As shown above in Table 5, compounds of the present invention have excellent inhibitory effect on the activities of HIV reverse transcriptase, having more than 70% reduction at the concentration of 1 μg/ml. Moreover, it is expected that compounds of the present invention, being non-nucleosidic, do not have problems such as toxicity and early development of resistant virus strains observed in the use of nucleoside substances. Furthermore, compounds of the present invention may be used together with nucleoside compounds since the former act on allosteric binding pockets while the latter act in the domain of polymerase activities.

As described above, compounds of the present invention have excellent inhibitory effect on the HIV enzyme activities in reverse transcription, which is a step in HIV replication. Based on the mechanism, these compounds are able to effectively control HIV proliferation and may be useful as therapeutics for prevention and treatment of AIDS.

<Experiment 4> Cytotoxicity Test

To determine if compounds of formula 1 exhibit cytotoxicity, invitro tests were carried out using HepG2 cells with MTT analysis method as generally known and the results are in Table 6 shown below.

TABLE 6 Cytotoxicity tests on HepG2 cells Cytotoxicity on HepG2 Compound IC₅₀ ¹⁾ MCD²⁾ Example 2 >100 100 Example 6 >100 100 Example 11 >100 100 ¹⁾IC₅₀: 50% Inhibitory Concentration (μg/ml) ²⁾MCD: Minimal Cytotoxic Concentration (μg/ml)

As shown above in Table 6, compounds used in the experiments have higher than 100 μg/ml for IC₅₀ and are considered to have little cytotoxicity.

<experiment 5> Acute Toxicity in Rats Tested Via Oral Administration

The following experiments were Performed to see if compounds of formula 1 have acute toxicity in rats.

6-week old SPF SD line rats were used in the tests for acute toxicity. Compounds in the examples of 1˜22 were suspended in 0.5% methylcellulose solution and orally administered once to 6 rats per group at the dosage of 2 g/kg/15 ml. Death, clinical symptoms, and weight change in rats were observed, hematological tests and biochemical tests of blood performed, and any abnormal signs in the gastrointestinal organs of chest and abdomen checked with eyes during autopsy. The results showed that the test compounds did not cause any specific clinical symptoms, weight change, or death in rats. No chance was observed in hematological tests, biochemical tests of blood, and autopsy. The compounds used in this experiment are evaluated to be safe substances since they do not cause any toxic change in rats up to the level of 2 g/kg and their estimated LD₅₀ values are much greater than 2 g/kg in rats.

INDUSTRIAL APPLICABILITY

As described above, novel 3-nitropyridine derivatives of formula 1 in the present invention have dramatic inhibitory effect on proliferation of HBV and of HIV with little side effect and may be useful as therapeutic agents for prevention and treatment of hepatitis B and AIDS.

Moreover, it is expected that compounds of the present invention, being non-nucleosidic, do not have problems such as toxicity and early development of resistant virus strains observed in the use of nucleoside substances. Furthermore, compounds of the present invention may be used together with nucleoside compounds since the former seem to act on allosteric binding pockets while the latter work in the domain of polymerase activities. 

What is claimed is:
 1. A 3-Nitropyridine derivative or pharmaceutically acceptable salt thereof as represented by formula 1:

Wherein,

R₁ is R₃ is piperazine which may be unsubstituted or substituted with alkyl group of C₁˜C₃; R₄ is H, straight or branched alkyl group with C₁˜C₄, or cycloalkyl group with C₃˜C₆; R₃ and R₄ both may consist of a piperazine, which is unsubstituted or substituted with a straight or branched alkyl group with C₁˜C₆, a straight or branched hydroxyalkyl group with C₂˜C₅, or hydroxy; R₂ is indazol-5-yl, or indazol-6-yl; and n is an integer between 0 and
 3. 2. Process for the preparation of the 3-nitropyridine derivative of claim 1, comprising the following two steps as represented in scheme 1: a) synthesizing a 3-nitropyridine derivative of formula 6 by reacting a 2-chloro-3-nitropyridine derivative of formula 4 with a 5-aminoindazole or 6-aminoindazole of formula 5 in the presence of a base at the temperature of 20-60° C.; and b) synthesizing a 3-nitropyridine derivative of formula 1 by reacting a 3-nitro-pyridine derivative of formula 6 synthesized in step 1 with amine compound of formula 7 at the temperature of 25-80° C.

Wherein, X is chloro or methoxy group; R₂ is indazol-5-yl, or indazol-6-yl; R₃ is piperazine, which may be unsubstituted or substituted with alkyl group of C₁˜C₃; R₄ is H, a straight or branched alkyl group with C₁˜C₄, or a cycloalkyl group with C₃˜C₆; R₃ and R₄ both nay consist of a piperazine, which is unsubstituted or substituted with straight or branched alkyl group with C₁˜C₅, straight or branched hydroxyalkyl group with C₂˜C₅, or hydroxy; and n is an integer between 0 and
 3. 3. A method of treating hepatitis B, comprising administering an affective amount of a compound of claim 1 to a patient in need thereof.
 4. A pharmaceutical composition comprising an effective amount of a compound of claim 1 and a pharmaceutically acceptable excipient.
 5. A 3-nitropyridine derivative of claim 1, wherein R₁ is


6. A process for preparing a 3-nitropyridine derivative of formula 1:

wherein, R₁ is

R₃ is piperazine which may be unsubstituted or substituted with alkyl group of C₁˜C₃; R₄ H, a straight or branched alkyl group with C₁˜C₄, or a cycloalkyl group with C₃˜C₆; R₃ and R₄ both may consist of a piperazine, which is unsubstituted or substituted with a straight or branched alkyl group with C₁˜C₅, a straight or branched hydroxyalkyl group with C₂˜C₅, or hydroxy; R₂ is indazol-5-yl, or indazol-6-yl; and n is an integer between 0 and 3; comprising reacting a compound of formula 6

wherein X is a chloro or methoxy group; with a compound of formula 7

at a temperature of 25-80° C. and under conditions sufficient to form the compound of Formula
 1. 